Fuel injection systems



Aug. 6, 1968 H. E. JACKSON FUEL INJECTION SYSTEMS 6 Sheets-Sheet 1 Filed Dec. 9, 1966 R v: R

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Aug. 6, 1968 H. E. JACKSON 3,395,683

FUEL INJECTION SYSTEMS Filed Dec. 9, 1966 6 Sheets-Sheet 2 1968 H. E. JACKSON 3,395,683

FUEL INJECTION SYSTEMS Filed Dec. 9, 1966 6 Sheets-Sheet 5 Aug. 6, 1968 H. E. JACKSON FUEL INJECTION SYSTEMS.

e Sheets-Sheet 4 Filed Dec. 9, 1966 O U F/GJ 6, 1968 H. E. JACKSON 3,395,683

FUEL INJECTION SYSTEMS Filed Dec. 9, 1966 6 Sheets-Sheet 5 Aug. 6, 1968 Filed Dec. '9, 1966 H. E. JACKSON FUEL INJECTION SYSTEMS 6 Sheets-Sheet 6 United States Patent 3,395,683 FUEL INJECTION SYSTEMS Harold Ernest Jackson, Plympton St. Mary, Devon, England, assignor of one-half to Petrol Injection Limited, Plympton, Plymouth, Devon, England, a British company Filed Dec. 9, 1966, Ser. No. 600,462 Claims priority, application Great Britain, Dec. 24, 1965, 54,794/ 65 Claims. (Cl. 123-140) ABSTRACT OF THE DISCLOSURE A fuel injection system of the continuous flow type for supplying a plurality of nozzles in the manifold of an internal combustion piston engine is controlled by certain engine parameters such as throttle position and engine speed. This system includes an engine driven pump with an output pressure proportional to engine speed delivering to a plurality of fuel metering circuits which control the pressure at the nozzles by throttling the fuel flow in a bypass to the pump inlet. Serially arranged metering devices in these circuits controlled by throttle position and pump pressure provide for selective operation in order to obtain the proper mixture ratio as engine volumetric efficiency varies over the engine speed range for each throttle position.

The present invention relates to continuous fuel injection systems for internal combustion engines and can be applied to systems of the continuous injection type.

It has been proposed to control fuel supply to injector devices of continuous injection systems by using a metering valve having a variable orifice controlled by a valve member operated by the engine throttle mechanism. This form of control results in fuel supply to the engine increasing steadily, for any particular throttle opening, with engine speed. However, on investigating the relationship between engine fuel requirements at different engine speeds, we have discovered that for any particular throttle opening, the fuel consumption increases steadily until a certain engine speed and thereafter continues to increase steadily but at a slower rate. The changeover speed at which this slower rate of fuel consumption occurs is quite marked and is dependent upon the particular throttle opening concerned, although no apparent relationship has been observed between throttle opening and this changeover speed. Thus, our investigations have indicated that at higher engine speeds, excess fuel is supplied to the engine when metering is effected by a metering orifice controlled by engine throttle opening and the present invention is concerned with more accurately relating fuel supplied to the engine to the actual requirements of the engine.

T o achieve this end, it is proposed to utilise a fuel metering valve having three orifices two of which are variable by respective metering valve members and the remaining metering orifice having a closure member, the seating force on which is adjustable. The two metering valve members and the closure member are actuated by separate control devices operably connected to a common operating member. The operating member is operable to vary the areas of the two metering orifices and to adjust the seating force exerted on the closure member of the third orifice. In use of such a metering valve, fuel is supplied to the valve at a pressure dependent on engine speed and the operating member is coupled to the engine throttle opening mechanism. For any particular throttle opening, over an initial range of engine speeds it is arranged that fuel pressure is insufiicient to unseat the closice ure member of the third orifice and that fuel is metered to the injector devices solely by a first one of the two variable metering orifices. At engine speeds lying above the initial range, it is arranged that the fuel pressure is sufficient to unseat the closure member of the third orifice and open a by-pass line from the first variable metering orifice, the by-pass line including the second of the variable metering orifices. Thus, when the closure member is unseated, fuel is supplied to the injector devices at a rate that increases with throttle opening but at a slower rate of increase than with the closure member closed. The two metering valve members can be controlled, for example, by cams contoured to obtain required rates of opening of the metering orifices with throttle opening and the closure member control devices can be controlled by a further cam to determine the relation between throttle opening .and seating force on the closure member so that the latter opens at desired speeds related to different throttle openings.

Thus, a continuous fuel injection system for an internal combustion engine having a throttle control mechanism, including a fuel circulation conduit system having supply and return branches, the supply branch including an engine drivable fuel pressurisation device operable to pressurise fuel flow in dependence on engine operating speed, and a plurality of injector devices, can incorporate, in accordance with the invention, a fuel metering valve mechanism having an inlet connected to the supply branch downstream of the fuel pressurising device, a first outlet connected to the injector devices, -a second outlet connected to the return branch, and a flow path connecting the inlet with the second outlet and a branch connection from the flow path to the first outlet. The flow path includes first and second metering valve devices connected in series flow relation with each other and with a check valve the opening pressure of which can be varied, the first metering valve device being located upstream of the second metering valve device and the check valve, and a control member common to the first and second metering valve devices and to the check valve, the control member being operably connected to the throttle control mechanism to control the first and second metering valve devices to permit increased fuel flow to the injector devices with increased throttle opening, and to determine the opening pressure of the check valve in dependence on throttle opening such that fuel can flow through the check valve and the second metering valve device only when fuel pressure exceeds the opening pressure of the check valve whereby when the check valve is open fuel fiow to the injector devices for any particular throttle opening increases with increasing engine speed (fuel pressure) at a slower rate than when the check valve is closed. The branch connection from the flow path between the inlet and second outlet, leading to the first outlet, can be downstream or upstream of the first metering valve device. When it is downstream, the first metering valve device is arranged to open with increasing throttle opening; when upstream, the first metering valve device is arranged to close with increasing throttle open- By way of example, the invention will be described in greater detail with reference to the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a system embodying the invention,

FIG. 2 shows a modification of part of FIG. 1,

FIG. 3 is a side view of a fuel flow control assembly suitable for use in the system shown in FIG. 1,

FIG. 4 is an end view of the assembly shown in FIG. 3,

FIGS. 5, 6 and 7 are sections on the lines VV, VI-VI, and VII-VII in FIG. 4,

FIGS. 8 and 9 are sections on the lines VIII-VIII and IX-IX in FIG. 5,

FIG. 10 is a section on the line XX in FIG. 3,

FIG. 11 is a top plan view of part of FIG. 4,

FIG. 12 is a section on the line XIIX1I in FIG, 11, and

FIG. 13 shows a detail section of part of FIG. 4.

FIG. 1 shows a continuous fuel injection system for an internal combustion engine, the system having a fuel supply conduit system including a supply line 1 including parallel branches 1A and 1B connected by lines 2A and 2B to a chamber 3 which in turn is connected by a line 4 to a distribution chamber 5. From the distribution chamber 5, lines 7, containing flow equalising restrictors 6, lead to fuel injector devices 8. Dowstream of their connections to the chamber 3, the supply line branches 1A and 1B are connected via fixed, adjustable check valves 9A and 9B to a fuel by-pass or return line 10.

Fuel is fed to the supply branch 1 by an engine driven pressurising pump 11 operable to pressurise fuel in the supply line in dependence on engine operating speed so that as engine speed increases, so does the fuel supply pressure. The pressurising pump is fed by a priming pump 12 that delivers fuel at a constant pressure determined by a vented relief valve 13, a lift pump 14 feeding the priming pump from the fuel tank 15 of the engine via a vapour separator 16. The by-pass line 10 is connected back to the tank 15 through a relief valve 17, having a vent 18, the vapour separator 16 and a check valve 19.

The injector devices 8 each have a housing 110 from which projects a tube 111 at the end of which is an outlet orifice 112. A resilient diaphragm 113 divides the housing into two chambers 114 and 115, the former communicating with one of the feed lines 7 and with the tube 111 and the latter containing a light spring 116 bearing on the diaphragm and urging a valve needle 117 carried by the diaphragm towards a seated position in the outlet orifice 112. The arrangement is designed such that inlet manifold vacuum does not interfere with fuel flow through the injector devices, particularly under conditions of low engine speed (i.e. low fuel pressure) and high inlet manifold vacuum (e.g. engine idling condition), the nozzles of the injector devices being disposed in the inlet manifold downstream of the throttle valve. Under these conditions fuel flow through the injector outlet orifice 112 might be such that the chamber 114 became exposed to inlet manifold vacuum which would interfere with fuel feed to the injector devices. However, when fuel pressure falls to such a level, the spring 116 seats the needle 117 in the outlet orifice 112 until fuel pressure in the chamber 114 acting on diaphragm 113 is sufficient to unseat the needle 117.

In operation of the system, as so far described, fuel is pumped through the supply line 1 at a pressure dependent on engine speed, the flow from the supply line dividing between the injector device 8 and the by-pass line 10 in proportions dependent on the relation between the flow restrictors A4, 6, B1 and the check valves 9A, 9B. By suitable choice of the flow resistances of these restrictors and check valves, circulation of fuel in the lines 1 and 10 can be maintained over the normal range of engine speeds whilst maintaining desired fuel supply to the injector devices.

The volume of fuel flow to the injector devices 8 is determined by flow restrictors in the supply line branches. As previously mentioned, the fuel requirements of the engine depend on the engine operating speed and on the engine loading, the latter being represented in this system by egine throttle opening.

When the engine is operating at any given throttle opening, as the engine speed increases the fuel volume requirement increases linearly until a speed is reached apparently unique for that particular throttle opening after which the fuel volume requirement increases at a slower rate. The rates of increase, both before and after the changeover point, appear to increase with increasing throttle opening but it has ben noted that the changeover point (although stable for any particular throttle opening) varies in a random manner as throttle opening is increased. Fuel is metered to the engine under these normal operating conditions and in accordance with engine requirements by a variable flow restrictor metering arrangement (to be described) in the supply line branch 1A in a manner that ensures accurate correlation of fuel feed with engine requirement, thereby leading to economical fuel consumption.

Apart from these normal engine operating conditions, an adequate supply of fuel must be supplied to the injector devices when the engine is running at idling speeds or running under low speed, lightly loaded conditions under which fuel pressure in the supply liner is low. This is achieved without detriment to the accuracy of the fuel metering by the variable flow restrictor arrange ment in the supply line branch 1A, by a metering flow restrictor arrangement, operable only under idling and low engine speed conditions, in the supply line branch 13. Further, when the engine is running under no-load, high speed conditions (i.e. overrun conditions), it requires no fuel and it is therefore arranged that, under these conditions, there is no fuel flow from the supply branches 1A or IE to the injector devices.

The construction of the metering arrangements in the supply line branches 1A and IE will now be described in greater detail to show how the above requirements are met.

The supply line branch 1A has an inlet section 21 passing through a variable flow restrictor A1 operable to determine fuel flow to the injector devices in dependence on engine throttle opening at engine speeds lower than the changeover points referred to previously. The variable restrictor A1 is connected by a line 22 to the feed line 2A and continues as a line 23 which divides into parallel-flow sub-branches 24 and 25. The sub-branch 24 has sections 26, 27 and 28, connected in series, sections 26 and 27 being connected by a variable check valve A2 and sections 27 and 28 being connected by a variable flow restrictor A3. The variable check valve A2 and the variable flow restrictor A3 are operable in response to engine throttle opening, the former opening at a fuel pressure corresponding to the changeover point associated with the throttle opening being used and the latter serving to regulate, in conjunction with the variable restrictor A1, fuel flow to the injector devices 8 at engine speeds higher than the changeover point for the throttle opening being used. The sub-branch 25 has sections 29 and 30 connected by the fixed flow restrictor A4. The sections 28 and 30 are each connected to a common section 31 leading to the check valve 9A.

The supply line branch 1B includes a chamber 32 containing a hollow plunger 33 carrying a valve needle 34. An inlet section 35 of the branch 1B leads to the chamber 32 on the rearward end of the plunger 33, that part of the chamber being connected to the forwards side of the plunger by a fixed flow restrictor B1. The front end of the chamber 32 has an outlet 36 providing a seat for the needle valve 34, the outlet being connected by a line 37 via a non-return valve B2 to the feed line 2B. The downstream end of the flow restrictor B1 also is connected through a line section 38 to the check valve 9B. The piston 33 contains a spring 39 which biases the needle valve 34 towards an unseated position.

The operation of the system will now be described for a variety of engine operating conditions. With the engine idling and the throttle closed (at low speed, no load), the variable restrictor A1 is closed and there is no fuel flow through the supply line branch 1A. In the supply line branch line 1B, flow passes through the chamber 32 and the fixed restrictor B1, and it is arranged that at idling speeds the fuel pressure acting on the plunger 33 is insufiicient to overcome the spring 39 and seat the needle valve 34. Thus fuel flow through the restrictor B1 divides, part flowing via outlet 36 and valve B2 to the feed line 2B and the remainder via line section 38 and restrictor 9B to the by-pass line 10. From the feed line 2B, fuel flows to the distribution chamber 5 and thence to the injector devices 8. The restrictor B1 and check valve 9B are so related that an adequate fuel flow to the injector devices is maintained under these engine idling conditions. The fuel flow paths under engine idling conditions are as follows, the reference numerals referring to the drawings:

BRANCH-RESTRI CTOR] CLO SED 38-9B BY PASS LINE 10 With the engine operating with the throttle partly open and at a low speed below the changeover point for that particular throttle opening, fuel passes through the restrictor A1 (which opens to a degree determined by the throttle opening), a portion of the fuel flow through the restrictor A1 passing to the feed line 2A (and hence to the injector devices 8) and the remainder flowing along line section 23. Since the engine speed is below the changeover point of the engine throttle opening setting, the check valve A2 remains closed and no fuel passes through subbranch 24 and the total fuel flow from the line section 23 passes via fixed restrictor A4 and check valve 9A, to the by-pass line 10. At low engine speeds, the pressure of fuel flowing from the supply line 1 to the chamber 32 in the supply line branch 1B is still insufficient to close the needle valve 34 so that fuel continues to flow to the injector devices 8 via the supply line branch 1B, in the same manner as under engine idling conditions, except that the volume of fuel flow through the branch 18 will reduce in proportion to the fuel flow through a branch 1A as the throttle, and variable restrictor A1, are opened. Under these conditions the fuel supply route to the injector devices 8 is as follows:

L- B RANCH-35-32-B1 INJECTOR DE \/'1 CES 847543 As engine speed increases, the fuel pressure in the chamber 32 of the supply line branch 13 increases until the needle valve 34 seats, closing the fuel supply route to the injector devices 8 via the feed line 2B. However, even with the valve 34 open, fuel supply to the injector devices 8 via the suply line branch 1B rapidly decreases in proportion to the fuel flow through the branch 1A as the throttle is opened, due to the reduction in flow resistance of the branch 1A, as restrictor A1 opens, relative to that of the branch 1B.

As engine speed increases further, with the throttle still partly open, and passes the changeover point for the throttle opening being used, fuel pressure in sub-branch 24 increases correspondingly and opens the check valve A2, and together with the variable restrictor A3 (which is open under these throttle conditions) the valve A2 establishes a flow path through sub-branch 24 in parallel with that through sub-branch 25. Thus, the flow resistance of the path between supply line branch 1A and 6 the by-pass line 10, via check valve 9A, is reduced 31 compared with the flow resistance at engine speeds below the changeover point for the throttle opening concerned, when the check valve A2 was closed. As the throttle is opened further, the variable restrictor A1 presents a decreasing flow resistance and in conjunction with the restrictor A3 adjusts fuel flow to the injector devices in accordance with engine requirements at the throttle opening ocncerned. The net effect is that with the check valve A2 open, for any particular throttle opening, increasing engine speed increases the fuel supply to the injector devices 8 via the supply line branch 1A, but at a decreased rate compared with the rate of increase with engine speed when the valve A2 is closed. At these higher engine speeds, the fuel pressure in chamber 32 seats the needle valve 34 and no fuel passes to the injector devices via supply line branch 1B. Under these conditions just described, with the check valve A2 open, and the throttle partly open, the fuel supply routes to the injector de- At full throttle opening, the variable restrictor A1 is fully open and the variable restrictor A3 may be closed. Since the supply line branch 1B also is closed, fuel supply to the injector devices is then determined solely by the variable restrictor A1. Under these full throttle conditions, with check valve A2 open and restrictor A3 closed, the fuel flow may be represented as follows:

FUEL

SUPPLY LINE BYPAS S L INE 10 l BRANCH-2l-A1 1A 0 L O S ED -BRANCH-35-32-B1-3e 1B 0 L o s ED L INE 10 Instead of connecting the feed line 2A to a common chamber 3 which in turn is connected to the distribution chamber 5, the feed lines 2A and 2B can be connected to separate distribution chambers each of which are connected to the individual lines 7 to the injector devices 8. Such an arrangement is shown in FIG. 2, the feed lines 2A and 23 leading to separate distribution chambers 40 and 41. The chamber is connected by individual conduits 42 containing non-return valves 43 to the lines 7 which contain flow restrictors 44. The distribution chamber 41 is connected via conducts 45 containing flow restrictors 46 to the lines 7, upstream of the restrictors 44. The check valves 9A and 9B shown in FIG. 1 as spring loaded ball valves, could be replaced by valve members having conical valve faces.

The variable restrictors A1 and A3 and the check valve A2 all are operated in response to engine throttle opening and, together with the restrictors A4 and B1 and fuel pressure responsive valve 34, can be constructed in a common housing. Such an arrangement is shown in FIGS. 3-13. In these figures, like references to those used in FIG. 1 have been used wherever possible in order to facilitate location of the various fuel flow paths through the supply line branches 1A and 1B and comparison with FIG. 1.

The fuel flow control assembly shown in FIGS. 3-13 has a housing 50 including an inlet port 51 for connection to the fuel supply line 1 of the system shown in FIG. 1. The inlet port 51 leads via a passage 21 to the variable flow restrictor A1 (FIGS. 5, 9) which includes a sleeve 52 in the bore of which is rotatable a closely fitting valve stem 53 having a drilling 54 extending partly along its length. The drilling 54 communicates with a metering orifice 55 in the form of an elongated slot extending transversely of the valve stem and having inwardly convergent walls which, projected, define a wedge shape. (Hereafter, this aperture, and others of like shape will be referred to as V-slots.) The V-slot 55 can register with a rectangular "aperture 56 in the sleeve wall, and as the valve stem 53 is rotated in the sleeve, the area of registration between the V-slot 55 and the aperture 56 is varied, so

changing the area of the metering orifice and hence the a flow resistance of the restrictor A1. The aperture 56 communicates with a passage 22 leading to the feed line 2A (FIG. 9) and to passages 23 and 23- (line 23, FIG. 1). Passage 23 leads via a passage 26 to the fuel pressure responsive check valve A2 (FIG. 8). This latter valve has a conical valve head 57 seated in an annular seating member 58 by a spring 59 partly disposed in a cup-shaped member 60 slidably mounted on a rod 61 secured in a wall of the housing 50. The valve A2 is disposed in a chamber 62 defined within the housing 50, a passage 27 leading from the chamber 62 and communicating with a further passage 27' (FIG. 9) leading to an inlet chamber 63 for the variable flow restrictor A3 (FIG. 6). The restrictor A3 is of like construction to that of the variable restrictor A1 and has a sleeve member 64 in the bore of which is a closely fitting rotatable valve stem 65. The valve stem 65 has a drilling 66 extending part of its length and communicating with a transverse V-slot 67 which registers with a rectangular aperture 68 in the sleeve 64 to define a metering orifice the area of which is adjusted by rotation of the valve stem 65. The open end of the valve stem 65 communicates with a passage 28 leading to an aperture 31 closed by a ball 69, urged towards a seated position by a spring 70 adjustable by a screw 71, which forms the adjustable check valve 9A. The spring 70 is disposed in a chamber 72 (with which the passage 28 communicates when the ball 69 is unseated) which communicates with an outet port 73 (FIGS. 4 and 12) for connection to the by-pass line 10 of FIG. 1.

The passage 23' (FIG. 9) leads to a passage 29 leading to a threaded insert 74 (FIG. 13) having a fine bore 75 (which constitutes the fixed flow restrictor A4) that in turn communicates with the passage 30 (common with passage 28) and thence via aperture 31 and the check valve 9A (FIG. 6) to the outlet port 73 (FIGS. 4 and 12).

The inlet port 51 (FIG. 5) also leads to the inlet passage 35 of the supply line branch 1B, the passage 35 communicating with the rear end of a cylindrical chamber 32 formed within the housing 5t) and'containing the hollow plunger 33 carrying the valve member 34.

The valve member 34 has a conical tip that can seat in the outlet 36 defined by a seating member 76. The plunger 34 is urged towards an unseated osition by the spring 39, the rearward travel of the plunger being limited by a stop member 77 threaded in the housing 50. The fixed restrictor B1 is defined by a fine bore passage 80 extending through the base or head of the plunger 33. As fuel presssure in the chamber 32 increases, so does the seating force on the plunger 33 and the valve member 34 which, when the seating force overcomes the spring 39, seats in the seating member 76 and closes the outlet 36. The latter communicates with a passage 37 leading via the non-return valve B2 (not shown in FIG. 5) to the feed passage 28 (FIGS. 5 and 9). On the forward side of the plunger 33, a passage 38 (FIG. 4) leads to an inlet passage 81 to the check valve 913 (FIG. 6). This restrictor has a ball 82 located in a chamber 83 and seated in the inlet passage 81 by a spring 84 that is adjustable by a screw 85. When the ball is unseated, the inlet passage 81 communicates with the chamber 83 from which a passage 86 leads to the outlet port 73 (FIGS. 4 and 12).

The closed ends of the valve stems 53 and 65 (forming part of the variable restrictors A1 and A3) have extensions 87 and 88 projecting into a chamber 89 in the housing 50, the extensions being secured to radially projecting adjustment clips 90 and 91 (operable to adjust the location of the transverse V-slots of the valve stems relative to the rectangular apertures in the valve sleeves) which carry rollers 92 and 93 extending parallel to the respective valve stems. The two rollers 92 and 93 engage with the cam surfaces of two cams 94 and 95 carried for rotation with a shaft 96 extending through the chamber 89 and projecting outwardly of the housing 50. The shaft also carries a cam 97 that engages with a roller 98 carried by a clip 99 that projects radially from a shaft 100 rotatably mounted in a wall 101, internally of the housing 50, and carrying a radially extending fork 102. The legs of the fork 102 straddle a reduced diameter of the cup-shaped member 60. The cam rollers 92, 93 and 98 are biased into engagement with their associated cams by springs 103 (FIG. 10).

As the shaft 96 is rotated, so are the cams 94, 95 and 97 resulting in rotation of the valve stems 53 and 65 and the shaft 100. By coupling the shaft 96 to the engine throttle control T (FIG. 3), the valves A1, A2 and A3 can be adjusted so that they operate in the manner described with reference to FIG. 1, the earns 94, 95 being arranged to rotate the valve stems 53 and 65 in appropriate senses and the cams 94, 95 and 97 being so shaped that desired fuel flow characteristics, dependent on engine throttle opening and accurately related to engine requirements, are obtained over the engine operating speed range, with appropriate changeover from relatively high increase in rate of fuel consumption with engine speeds, for any particular throttle opening, below the changeover point and a relatively slower rate of increase with engine speeds above the changeover point, the latter being determined by the cam 97 varying the seating force applied to the valve head 57.

I claim:

1. A liquid metering valve mechanism having an inlet and first and second outlets, liquid flow path means connecting the inlet and the second outlet and branch connection means connecting the flow path to the first outlet, the said flow path means including first and second metering valve devices located in series flow relation with each other and with a check valve the opening pressure of which can be varied, the said first metering valve device and said branch connection each being located upstream of the said second metering valve device and the said click valve, and a common control member operably associated with the said first and second metering valve devices and to the said check valve, the said control member being operable to determine the opening pressure of the said check valve and to control the said first and second metering valve devices such that liquid flow from the said first metering valve device to the said second outlet can occur only at pressures of said liquid above the opening pressure of the said check valve as determined by the said control member.

2. A metering valve mechanism according to claim 1, further including a by-pass flow passage containing a fiow restrictor connected in parallel flow relation with the said second metering valve device and the said check valve.

3. A metering valve mechanism according to claim 2, in which the said flow path means includes a further check valve connected downstream of the said by-pass fiow passage.

4. A liquid metering valve mechanism having an inlet and first and second outlets, first and second variable area orifice metering valve devices and a check valve the seating force on which is adjustable, the said inlet being connected with the said first outlet by the said first metering valve device and being connected with the said second outlet by the said first and second metering valve devices and the said check valve in series with each other the said first metering valve device being located upstream of the said second metering valve device and the said check valve, and a common control member adjustable in position to control the orifice areas of the said first and second metering valve devices and to vary the seating force on the said check valve such that the check valve opens only at liquid pressures above a selected pressure determined by the control member position.

5. A valve mechanism according to claim 4, in which the effective orifice areas of the said first and second metering valve devices are determined by respective valve members rotatable by operation of the common control member.

6. A valve mechanism according to claim 5, in which each of the said rotary valve members is an elongated cylindrical member rotatably mounted in a closely fitting sleeve having an aperture in the wall thereof, the said cylindrical member having an internal passage communicating with a transverse slot in the wall of the said cylindrical member, the said transverse slot changing in width along its length such that rotation of the said cylindrical member changes the area of the said transverse slot that registers with the said sleeve aperture.

7. A valve mechanism according to claim 5, in which the common operating member is rotatably mounted and carries first and second cams that engage with respective cam followers carried by the said rotary valve members of the first and second metering valve devices, such that rotation of the operating member causes rotation of the said valve members in a manner determined by the cam surfaces of the said first and second cams, and in which the said common operating member also carries a third cam engageable with a cam follower carried by a coupled device with the said check valve such that rotation of the said common operating member causes the said coupling device to vary the seating force on the said check valve in -a manner determined by the cam surface of the said third cam.

8. A valve mechanism according to claim 4, in which the said second metering valve device and the said check valve are connected in parallel with a by-pass flow passage containing a flow restrictor.

9. A valve mechanism according to claim 8, including a second check valve connected in the flow path between the inlet and the second outlet downstream of the bypass flow passage.

10. A valve mechanism according to claim 9, in which the inlet is also connected to the second outlet by a second flow path in parallel with the said flow path containing the said first and second metering valve devices and the said variable check valve, the said second flow path including a fixed flow restrictor, and a closure valve device located downstream of the fixed restrictor connecting said second fiow path to the said first outlet, the said closure valve device having a pressure responsive control member exposed to liquid fiow in the said second flow path upstream of the said fixed restrictor such that the said closure device is closed at liquid flow pressures above a predetermined value.

11. A valve mechanism according to claim 10, in which the said closure valve device includes a chamber forming part of the second flow path and containing a plunger carrying a closure valve member, and means resiliently biasing said member towards an open position, the said plunger being exposed to liquid flow pressure upstream of the said fixed restrictor to urge the said plunger and said closure valve member towards a closed position.

12. A valve mechanism according to claim 11, further including a third check valve connected in the said second flow path downstream of the fixed flow restrictor and upstream of the said closure valve device.

13. A continuous fuel injection system for an internal combustion engine having a throttle control mechanism, including a fuel circulation conduit system having supply and return branches, the said supply branch including an engine drivable fuel pressurising device operable to pressurise fuel flow in dependence on engine operating speed, and a plurality of injector devices, the said conduit system also including a fuel metering valve mechanism according to claim 2, the said inlet of the metering valve mechanism being connected with the said supply branch downstream of the said fuel pressurising device, the said first outlet of the metering valve mechanism being connected to the injector devices and the said second outlet of the metering valve mechanism being connected to the return branch, and means operably coupling said engine throttle control mechanism with the said common control member of the valve mechanism to cause increased fuel flow to the injector devices with increased throttle opening, :and such that the degree of said throttle opening causes the common control member to determine the fuel pressure necessary to open the said variable check valve of the metering valve mechanism to permit fuel flow through the said variable check valve and the said second metering valve device to the said second outlet whereby when the said variable check valve is open the fuel flow to the said injector devices for any particular said throttle opening increases with increasing engine speed at a slower rate than when the said variable check valve is closed.

14. A continuous fuel injection system for an internal combustion engine having a throttle control mechanism, including a fuel circulation conduit system having supply and return branches, an engine drivable fuel pressurising device connected in the supply branch and operable to pressurise fuel flow in dependence on engine operating speed, and a plurality of fuel injector devices, a fuel metering valve mechanism according to claim 7, in which the said metering valve mechanism inlet is connected to the said fuel supply branch downstream of the said fuel pressurising device, in which the said first outlet is connected to the respective said fuel injector devices and the said second outlet is connected to the said fuel return branch, and in which the said common control member is operably coupled to the said engine throttle control mechanism to open the said first metering valve device with increasing throttle opening, and such that the degree of said throttle opening causes the common control member to determine the fuel pressure necessary to open the said variable check valve of the metering valve mechanism to permit fuel flow to the said second outlet through the said variable check valve and the said second metering valve device whereby for any particular said throttle opening when the said variable check valve is open fuel fiow to the said injector devices increases with engine speed at a slower rate than when the said variable check valve is closed.

15. A continuous fuel injection system for an internal combustion engine having a throttle control mechanism, including a fuel circulation conduit system having supply and return branches, an engine drivable fuel pressurising device connected in the supply branch and openable to pressurise fuel flow in dependence on engine operating speed, and a plurality of fuel injector devices, a fuel metering valve mechanism according to claim 10, in which the said inlet of the metering valve mechanism is connected to the said fuel supply branch downstream of the said fuel pressurising device, the said first outlet is connected to the respective said fuel injector devices, and the said second outlet is connected to the said fuel return branch, and in which the said common control member of the said valve mechanism is operably coupled to the said engine throttle control mechanism to open the said first metering valve device with increasing throttle opening, and such that the degree of said throttle opening causes the said common control member to d termine the fuel pressure necessary to open the variable check valve of the metering valve mechanism to permit fuel flow through the said variable check valve and the said second metering valve device to the said second outlet, whereby for any particular said throttle opening when the said variable check valve is open fuel flow to the said injector devices increases with increasing engine speed at a slower rate than when the said variable check valve is closed, and in which the said closure v-alve device in the second flow path of the metering valve mechanism remains open to permit fuel flow via the said second flow path to the said first outlet only at fuel pressures corresponding to a predetermined range of engine speeds at the lower end of the engine operating speed range and occupying a small proportion of the overall engine operating speed range.

References Cited UNITED STATES PATENTS 2,374,844 5/ 1945 Stokes 123-1403 2,880,714 4/1959 Clark 123-1403 3,311,099 3/1967 Beaber 123-119 3,327,760 6/1967 Crawford 123-119 XR FOREIGN PATENTS 900,631 12/ 1953 Germany.

LAURENCE M. GOODRIDGE, Primary Examiner. 

